Vibrating mirror element, distance measuring apparatus, and projector

Abstract

A vibrating mirror element includes a drive control portion configured to control the driving of a correction drive portion to keep the turning angle velocity of a mirror portion substantially constant by oscillating the mirror portion about an axis at a non-resonance frequency in a direction opposite to a direction in which a resonant drive portion oscillates the mirror portion.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a vibrating mirror element, a distance measuring apparatus, and a projector, and more particularly, it relates to a vibrating mirror element, a distance measuring apparatus, and a projector each including a resonant drive portion and a drive control portion controlling the driving of the resonant drive portion.[0003]2. Description of the Background Art[0004]A vibrating mirror element, a distance measuring apparatus, and a projector each including a resonant drive portion and a drive control portion controlling the driving of the resonant drive portion are known in general, as disclosed in Japanese Patent Laying-Open No. 2008-009446.[0005]Japanese Patent Laying-Open No. 2008-009446 discloses an image-forming apparatus having a resonance type light-deflector (vibrating mirror element) for deflecting a laser light, a driving portion (resonant drive portion) for oscillating a first movable e...

AI Technical Summary

Benefits of technology

[0009]In the vibrating mirror element according to the first aspect of the present invention, as hereinabove described, the driving of the resonant drive portion is controlled to oscillate the mirror portion about the axis at the resonance frequency, and the driving of the correction drive portion is controlled to keep the turning angle velocity of the mirror portion substantially constant by oscillating the mirror portion about the axis at the non-resonance frequency in the direction opposite to the direction in which the resonant drive portion oscillates the mirror portion, whereby the driving of the correction drive portion can be controlled to oscillate the mirror portion at the arbitrary non-resonance frequency unlike the case where the driving of the correction drive portion is controlled to vibrate the mirror portion at the resonance frequency and a frequency of an even multiple of the resonance frequency, and hence the degree of freedom of control of the correction drive portion can be increased. Consequently, the turning angle velocity of the mirror portion can be kept substantially constant during a substantially entire period in one cycle of the oscillation. Furthermore, in the case where a vibrating mirror element in which the turning angle velocity is not constant is applied to a distance measuring apparatus, for example, a laser light source must be pulse-driven in order to emit laser light at a regular angular interval, and the pulse-drive timing must be temporally corrected. On the other hand, according to the present invention, the turning angle velocity of the mirror portion can be kept substantially constant during the substantially entire period in one cycle of the oscillation, and hence a distance measuring apparatus requires no control means configured to perform pulse control on laser light, so that the structure of the distance measuring apparatus can be simplified.

[0034]In the projector according to the third aspect of the present invention, as hereinabove described, the driving of the resonant drive portion is controlled to oscillate the mirror portion about the axis at the resonance frequency, and the driving of the correction drive portion is controlled to keep the turning angle velocity of the mirror portion substantially constant by oscillating the mirror portion about the axis at the non-resonance frequency in the direction opposite to the direction in which the resonant drive portion oscillates the mirror portion, whereby the driving of the correction drive portion can be controlled to oscillate the mirror portion at the arbitrary non-resonance frequency unlike the case where the driving of the correction drive portion is controlled to vibrate the mirror portion at the resonance frequency and a frequency of an even multiple of the resonance frequency, and hence the degree of freedom of control of the correction drive portion can be increased. Consequently, the projector in which the turning angle velocity of the mirror portion can be kept substantially constant during a substantially entire period in one cycle of the oscillation can be provided.

Problems solved by technology

In the resonance type light-deflector disclosed in Japanese Patent Laying-Open No. 2008-009446, however, the period of time when the turning angle velocity of the first movable element can be substantially constant is disadvantageously limited whereas the first movable element is configured such that the turning angle velocity is substantially constant during the prescribed period of time in one cycle of the oscillation.

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